如何在 Python 中模拟 sqlite3.connect

Question

我在 Anaconda 环境下使用 Python 3.3。

我想模拟 sqlite3.connect。例如在MyTests（见下文）中，我想test_sqlite3_connect返回字符串connection而不是实际sqlite3.Connection对象。

我试过修补它，但这不起作用。

from unittest.mock import patch
import unittest

import sqlite3

@patch('sqlite3.connect')
def sqlite3_connect(self,connection_string):
    print('connect with : {0}'.format(connection_string))
    return 'connection '

class MyTests(unittest.TestCase):

    def test_sqlite3_connect(self):

        print('testing connection')

        dbc = DataBaseClass()


class DataBaseClass():

    def __init__(self):
        print('initialising database class')
        self.connection = sqlite3.connect('test database')

Answer 1

我设法使用快速指南部分的信息解决了这个问题

http://www.voidspace.org.uk/python/mock/

下面的代码展示了两种模拟 sqlite3.connect 的方法。

''' An example of how to mock the sqlite3.connection method '''

from unittest.mock import MagicMock,Mock
import unittest
import sqlite3

class MyTests(unittest.TestCase):

    def test_sqlite3_connect_success(self):

        sqlite3.connect = MagicMock(return_value='connection succeeded')

        dbc = DataBaseClass()
        sqlite3.connect.assert_called_with('test_database')
        self.assertEqual(dbc.connection,'connection succeeded')


    def test_sqlite3_connect_fail(self):

        sqlite3.connect = MagicMock(return_value='connection failed')

        dbc = DataBaseClass()
        sqlite3.connect.assert_called_with('test_database')
        self.assertEqual(dbc.connection, 'connection failed')

    def test_sqlite3_connect_with_sideaffect(self):

        self._setup_mock_sqlite3_connect()

        dbc = DataBaseClass('good_connection_string')
        self.assertTrue(dbc.connection)
        sqlite3.connect.assert_called_with('good_connection_string')

        dbc = DataBaseClass('bad_connection_string')
        self.assertFalse(dbc.connection)
        sqlite3.connect.assert_called_with('bad_connection_string')

    def _setup_mock_sqlite3_connect(self):

        values = {'good_connection_string':True,
                  'bad_connection_string':False}

        def side_effect(arg):
            return values[arg]

        sqlite3.connect = Mock(side_effect=side_effect)


class DataBaseClass():

    def __init__(self,connection_string='test_database'):        
        self.connection = sqlite3.connect(connection_string)